Uridine diphosphate glucose: glycoprotein glucosyltransferase (UGGTase) is an enzyme found in the endoplasmic reticulum which catalyzes the glucosylation of glycoproteins containing glucose free high mannose oligosaccharides. UGGTase is a key enzyme in the calnexin/calreticulin cycle acting as a protein folding sensor. Those glycoproteins which are misfolded or incompletely folded are selectively glucosylated by UGGTase such that they remain ligands for calnexin/calreticulin and remain in the endoplasmic reticulum until properly folded. Inhibitors of UGGTase may be used to treat several pathological conditions including viral infection, cystic fibrosis, emphysema, scurvy, hereditary hyperlipemia, Glanzman's thromobostenia, congenital sucrose-isomaltese deficiency, hexosaminidase A deficiency, Marfan's syndrome, fibrinogen storage disease, nanomelia (in chicken), .alpha.-antichymotrypsin deficiency, von Willebrand's disease, retinitis pigmentosa, and glioblastoma.